In an Operating System (iOS) system, in order to ensure that a program may run steadily and smoothly, some limitations are made on the program. For instance, a non-system level program is not allowed to run in the background. Therefore, if the program is switched to run in the background, the program may be hung up by the system in a short time and the program may stop running. Programs cannot access each other's resources. Therefore, data exchange between programs (or processes) cannot be performed.